Pacific Dawn was in Port Vila when the accident happened.
The boat visited Honiara early this year.
Shine Lawyers’ senior solicitor Thomas Janson said legal “waivers” signed by the passengers who took the onshore excursion of Port Vila were unenforceable under Australian Consumer Law.
He said providing the passengers had booked their cruise in Australia they would be covered by the law.
“The Australian Consumer Law is a powerful and consumer friendly piece of legislation,” said Mr Janson.
“The ACL doesn’t allow an unfair contract term that limits or attempts to limit the liability of one party for the act of its agent.
“This means that P&O cannot attempt to say that it is not liable to passengers through a contractual term for the actions of the tour bus operator.”
An investigation is underway into the crash between the tour bus and a commuter bus.
Ten of the 11 Australians on board the excursion bus were seriously injured, and three locals on the other vehicle were killed.
Carnival Australia Executive Chairman Ann Sherry said on Tuesday that whether or not the passengers were wearing seatbelts would form part of the investigation.
Mr Janson said P&O may be able to assert that passengers were “contributorily negligent” in not wearing seatbelts.
“However this depends on whether seatbelts were inside the bus and fitted to the seats,” he said.
Grounds on which the passengers could sue included economic loss, pain and suffering, past and future treatment costs and domestic assistance.
“You could be looking at a considerable sum,” Mr Janson said.
A statement posted by P&O said all ten people injured had now been brought to a Brisbane hospital, and the most seriously injured — an 11-year-old boy — was no longer critical.
“He and his Mum are being cared for in the same hospital room,” said the statement.
“A P&O Care team member is with the family.”
Assistance was also being provided for the families of the local Ni Van people who lost their lives in the crash.
“P&O is looking at other ways to assist further in the coming days,” said the statement.
By Robyn Ironside
News Corp Australia Network